1. Field of the Invention
The present invention relates to an electron emission device and an electron emission display using the electron emission device. More particularly, the present invention relates to an electron emission device configured to enhance electron emission efficiency and an electron emission display using the same.
2. Description of the Related Art
Generally, electron emission devices may be classified according to whether a hot cathode technology or a cold cathode technology is employed to generate electron emission. There are several types of cold cathode-based electron emission devices including, e.g., Field Emission Array (FEA) devices, Surface-Conduction Emission (SCE) devices, Metal-Insulator-Metal (MIM) devices and Metal-Insulator-Semiconductor (MIS) devices.
The FEA devices typically include electron emission regions, and cathode and gate electrodes as driving electrodes. The electron emission regions may be formed of, e.g., a material having a relatively low work function or a relatively large aspect ratio, such as carbonaceous materials or nanometer-sized materials, so that electrons can be effectively emitted when an electric field is applied thereto under a vacuum atmosphere. A region where the cathode and gate electrodes cross may have one or more electron emission regions positioned therein to form a single electron emission element. The electron emission device may include a first substrate having a plurality of the electron emission elements, which may be arranged, e.g., in an array. The electron emission device may be coupled to a light emission device to form an electron emission display. The light emission device may include a second substrate having a phosphor layer, a black layer and an anode electrode. The light emission device may be positioned to face the electron emission device.
In detail, an FEA electron emission display may include a first substrate on which cathode electrodes, an insulating layer and gate electrodes are stacked in sequence. The gate electrodes and the insulating layer may have openings therein that partially expose surfaces of the cathode electrodes. The electron emission regions may be positioned on surfaces of the cathode electrodes that are exposed through the openings.
For each FEA electron emission element, the cathode electrode and the gate electrode may be operated together to generate electron emission from the electron emission region(s) included in the electron emission element. The cathode electrode may provide an electric current that supplies electrons to the electron emission regions for the electron emission. The gate electrode may provide a control signal to control the electron emission by forming an electric field around the electron emission regions, where the electric field results from a voltage difference between the gate and cathode electrodes.
A drawback to the above-described FEA electron emission device is that it may be difficult to properly form the electric field around the electron emission regions. In particular, the electric field may be concentrated on a local region of each electron emission region, e.g., on an outer top edge of the electron emission region, which is closest to the gate electrode. As a result, electrons may be primarily emitted from the local region of the electron emission region, which may lower the efficiency of electron emission. In order to compensate for the lower efficiency, the driving voltage applied to the electron emission device may be increased. However, the increased driving voltage may reduce the service life of the electron emission regions. Therefore, the above-described FEA electron emission device may not be suitable for a high-efficiency electron emission display.